12 research outputs found
Advanced prevention against icing on high voltage power lines
Historical meteorological data indicates, that our weather is becoming more and more extreme. For the
electrical utility operators (Distribution System Operators - DSOs and Transmission System Operators -
TSOs), these changes arise in new operation challenges that need to be addressed. For example, frequent icing
phenomenon affects all the components of the power line by a significant mechanical overload: it endangers
the conductors, the insulators and the towers, as well. The result is often fatal and beside serious failures, it
effects on operators’ decisions. These not only endanger the reliability of electrical grids by the loss of a power
line for weeks or even months, but in general, the safety in the surroundings of the power line. As technology
advances, we will be able to collected, analyses and predict very large databases in the field of meteorology
and electrical engineering. The ability of processing mentioned data, combined with know-how results in the
capacity to operate power lines at their thermal limits during different ambient parameters. This technology
called Dynamic Line Rating (DLR) – is not only a great way to increase the transmission capacity of a given
line, but can also be effectively used to prevent, or even solve icing-related issues. Higher currents result in
higher Joule-heats, that consequently heat the conductors. If limits can be reached or approached, icing can be
prevented. If prevention is not possible, detection and removal of ice layer is necessary. The proper handling
of this icing issues, requires advanced algorithms (expert systems) and reliable measuring equipment. The
combination and synchronization between algorithms, weather service and measuring equipment is the key of
the successful operation. An EU H2020 financed project called FLEXITRANSTORE has just been launched
to develop a cross-country co-operation, with objective to improve anti-icing and de-icing solutions. To
establish and analyse different solutions, the project includes several universities, TSOs and DSOs. To solve
mentioned icing issues Budapest University of Technology and Economics’ (BME) developed an advanced
neural-network based algorithm which use OTLM system. It is planned to install and demonstrate the
capabilities of this new technology on the DSOs grid (Electro Ljubljana - ELJ). Besides the introduction of
DLR and icing, this paper also focuses on the preparation/organisation of co-operation between different
companies and universities
The use of cyclic DJ q as a parameter for fatigue initiation of X52 steel
International audienceThe concept of DJ cyclic has been extended to fatigue initiation emanating from notch. The parameter is then named DJ q. Validation of this parameter is made by fatigue tests made on Roman tile specimens made in X52 pipe steel. Here, fatigue initiation is detected by acoustic emission. It has been found that the fatigue initiation decreases after hydrogen absorption. This can be explained by interaction of hydrogen and plasticity as can be seen for tensile and fracture behaviour of X52 steel after introduction of hydrogen
The influence of residual stresses on fracture behavior of Pipe Ring Notched Bend specimen (PRNB)
Fracture toughness analysis of a ductile steel by means of 3D surface displacements
The standards for characterization of fracture toughness of metals are focused on the calculation of fracture parameters based only on in-plane displacements of the specimen tested. Although fracture is a three-dimensional problem, out-of-plane displacements of the specimen tested are not mentioned in those documents. Since three-dimensional displacement measurement is available, it is worth investigating its potential uses in fracture tests. In this work, the fracture toughness of a structural steel was assessed through standard tests, measuring three-dimensional surface displacements. An alternative Crack Tip Opening Displacement calculation was introduced. The fracture initiation was inferred from the out-of-plane displacements, finding good agreement with results from R-curves.Fil: Paolinelli, Luciano Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Carr, Gustavo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Gubeljak, N.. University of Maribor; EsloveniaFil: Predan, J.. University of Maribor; EsloveniaFil: Chapetti, Mirco Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin
Micromechanical analysis of constraint effect on fracture initiation in strength mis-matched welded joints
In this paper the micromechanical approach to ductile fracture was applied in a study of constraint effect crack growth initiation in mismatched welded joints. The single edged- notched bend specimens (precrack length ▫▫) were experimentally and numerically analysed. The coupled micromechanical model prposed by Gurson, Tvergaard and Needleman was used. Constraint effect was tested by varying widths of the welded joints (6, 12 and 18 mm). HSLA steel was used as the base metal in a quenched and tempered condition. The flux-cored arx-welding process in shielding gas was used. Two different fillers were selected to obtain over- and undermatched weld metal. The micromechanical parameters used in prediction of the crack growth initiation on precracked specimen were calibrated on a round smmoth specimen. The difference in fracture behaviour between over- and undermatched welded joints obtained in experimental results was followed by numerical computationsof void volume fraction in front of the crack tip
Micromechanical analysis of constraint effect on fracture initiation in strength mismatched welded joints
In this paper the micromechanical approach to ductile fracture was applied in a study of constraint effect on crack growth initiation in mismatched welded joints. The single-edged notched bend specimens (precrack length a 0/W=0.32) were experimentally and numerically analyzed. The coupled micromechanical model proposed by Gurson, Tvergaard and Needleman was used. Constraint effect was tested by varying widths of the welded joints (6, 12 and 18mm). High-strength low-alloyed (HSLA) steel was used as the base metal in a quenched and tempered condition. The flux-cored arc-welding process in shielding gas was used. Two different fillers were selected to obtain over- and undermatched weld metal. The micromechanical parameters used in prediction of the crack growth initiation on precracked specimen were calibrated on a round smooth specimen. The difference in fracture behavior between over- and undermatched welded joints obtained in experimental results was followed by numerical computations of void volume fraction in front of the crack tip
Micromechanical analysis of constraint effect on fracture initiation in strength mismatched welded
In this paper the micromechanical approach to ductile fracture was applied in a study of constraint effect on crack growth initiation in mismatched welded joints. The single-edged notched bend specimens (precrack length a(0)/W=0.32) were experimentally and numerically analyzed. The coupled micromechanical model proposed by Gurson, Tvergaard and Needleman was used. Constraint effect was tested by varying widths of the welded joints (6, 12 and 18mm). High-strength low-alloyed (HSLA) steel was used as the base metal in a quenched and tempered condition. The flux-cored are-welding process in shielding gas was used. Two different fillers were selected to obtain over- and undermatched weld metal. The micromechanical parameters used in prediction of the crack growth initiation on precracked specimen were calibrated on a round smooth specimen. The difference in fracture behavior between over- and undermatched welded joints obtained in experimental results was followed by numerical computations of void volume fraction in front of the crack tip
Welded Joints Behaviour in Service with Special Reference to Pressure Equipment
Quality and structural integrity of welded pressure equipment are defined by The Pressure Equipment Directive (97/23/EC). The problem is complex, due to welded joint imperfections, matching effect, heterogeneity of microstructure and material properties. Equipment can be fit for service with defects unacceptable by codes, what should be proved by fracture mechanics approach, especially for cracks in the heat-affected-zone